1. Field
The presently disclosed subject matter relates to a vehicle headlight of a projector type, and more particularly to a projector headlight for a low beam having a favorable light distribution pattern that can conform to a light distribution standard for a headlight with respect to a contrasting difference between the upper and lower sides of a horizontal cut-off line in the light distribution pattern.
2. Description of the Related Art
A projector headlight for a low beam and/or a high beam is frequently incorporated into a vehicle lamp including a position lamp, a turn-signal lamp, etc. The projector headlight may allow a light-emitting area thereof to be reduced and therefore allows a vehicle lamp that includes such a projector headlight to be minimized in comparison with other types of headlights. In addition, when an LED is used as a light source for the projector headlight, a battery friendly and small projector headlight can be achieved.
A projector headlight is also disclosed in Applicant's co-pending patent application, U.S. patent application Ser. No. 12/794,488, filed on same date, Jun. 4, 2010, which is hereby incorporated in its entirety by reference.
A conventional projector headlight for use as a low beam light is disclosed in patent document No. 1 (Japanese Patent Application Laid Open JP2003-317513). FIG. 12 is a schematic side cross-section view depicting a structure for the conventional projector headlight in patent document No. 1, and an LED is used as a light source of this projector headlight.
According to the conventional projector headlight 50 shown in FIG. 12, the projector headlight 50 includes: an LED light source 52; an elliptical reflector 54 in which a first focus thereof is located near the LED light source 52; a projector lens 56 which has a focus thereof located near a second focus of the elliptical reflector 52; and a shade 58 located near the focus of the projector lens 56. Thus, an optical axis Z50 approximately corresponds with the respective optical axes of the elliptical reflector 54 and the projector lens 56, and the LED light source 52.
In the projector headlight 50, light emitted from the LED light source 52 is reflected on the elliptical reflector 54 and can be emitted in a forward direction of the projector headlight 50 via the projector lens 56. In this case, a part of the light that is reflected on the elliptical reflector 54 can be shielded by the shade 58. Accordingly, the projector headlight 50 can form a light distribution pattern for a low beam including a cut-off line in accordance with a top shape of the shade 58.
However, because the shade 58 is substantially located at the focus of the projector lens 56, a contrasting difference between the upper and lower sides of a horizontal cut-off line of an oncoming lane and of a driving lane in the light distribution pattern tends to become too clear. When the light-emitting area of the projector headlight 50 becomes smaller and/or the brightness thereof becomes brighter using a high power light source and/or the like, the contrasting difference may be especially enhanced and too clear. Thus, the projector headlight 50 may include a problem in that the excessive contrasting difference thereof causes a decrease of visibility in some cases.
In order to reduce the contrasting difference, another conventional projector headlight for use as a low beam light is disclosed in patent document No. 2 (Japanese Patent Application Laid Open JP2008-262755). FIG. 13 is a schematic side cross-section view depicting a projector lens for the other conventional projector headlight that is disclosed in patent document No. 2. According to this projector headlight, on a surface towards a focus F68 of a projector lens 66, convex surfaces are provided as a means to diffuse light that forms a cut-off line in a light distribution pattern. The convex surfaces may blur the cut-off line, and therefore may improve visibility in the light distribution pattern.
The above-referenced Patent Documents are listed below and are hereby incorporated with their English abstract in their entirety.
1. Patent document No. 1: Japanese Patent Application Laid Open JP2006-317513
2. Patent document No. 2: Japanese Patent Application Laid Open JP2008-262755
However, when diffusing light by a surface of the projector lens like the projector lens that is disclosed in patent document No. 2, the surface of the projector lens may effect a change in light other than that near the cut-off line, and therefore may cause a decrease of a maximum light intensity and/or a glare. In addition, it may be difficult to form convex surfaces on the surface of the projector lens during a manufacturing process, especially when the projector lens is made of a glass material, it may be very difficult because the process may become the last process.
The disclosed subject matter has been devised to consider the above and other problems, characteristics and features. Thus, an embodiment of the disclosed subject matter can include a projector headlight for a low beam having a favorable light distribution pattern that can conform to a light distribution standard for headlights with respect to a contrast difference between the upper and lower sides of a horizontal cut-off line. In this case, various light sources such as a semiconductor light source, an HID lamp, a halogen bulb and the like can be employed as a light source with a simple structure.